Capillary electrophoretic separation of organophosphonic acids using borate esterification and direct UV detection

One major challenge in the analysis of small ions by capillary zone electrophoresis (CZE) is detection. The most common commercially available detector for CZE is based on UV absorbance. For many small molecules, however, little UV absorbance occurs above 210 nm, limiting the usefulness of this detection method. Carbohydrates, alcohols and amides have been separated and directly detected by complexation with sodium borate. It has been shown that these complexes have UV absorbances in the range of 220 to 280 nm, whereas the analytes alone are UV transparent at energies less than 200 nm. Separation and direct detection of organophosphonic acids using sodium borate as both a buffer and derivatization agent is demonstrated. Detection limits on the order of nanograms are reported with separations that exhibit 10 000 to 1 740 000 theoretical plates. The ultraviolet, infrared, nuclear magnetic resonance and mass spectra of various borate/phosphonic acid esters are explored.